it gets complicated rather quickly - it's formulation dependent (ie how much cocoa butter you have will directly impact it). drilling down to cocoa butter, since cocoa butter's triglyceride profile is different all around the world, each butter's specific heat will be different. and then you overlay the impact of tempering and crystal form (each of the 6 different forms have their own specific heat...). So there's no quick and easy answer if you're looking for an accurate number 8-)
The easiest thing to do, in my opinion, is average cocoa butter - a good ballpark figure for liquid cocoa butter at 40C would be, oh, about 0.5 cal/g. If you need to estimate SH in solid form, i'd start with 0.52 cal/g (20C, assuming predominance of form V).
Call me a luddite here, but wouldn't other variables come into play? I'm thinking variables such as:
1. Heat loss created by the space and air flow between the heating element and the medium containing the chocolate, OR in the case of water being the medium carrying the heat (which is the case in almost all commercial chocolate equipment), how much energy is required to bring the water up to the correct temperature, and keep it there, and what is the rate of loss/transfer from the water, through the holding vessel, and to the Chocolate?
2. What is the medium the chocolate is being held in?
3. Does the medium reflect heat, or absorb heat. (In this case, think of simple table top tempering units that utilize a steel bowl and lightbulbs as a heat source. There's a reason the back of the bowls are all painted flat black.
4. What form is the chocolate in? Is it in a big block, or is it in small chips?
5. How much of that surface is actually in direct contact with the heat. The larger the surface contact with the heat source, the quicker the melt.
I've melted enough chocolate in the last two years to say definitively that I can melt 10kg of chocolate in one hour with four 110 watt lightbulbs. My staff do that almost every morning.
In my experience, sometimes "let's try a number of variations and see what happens" works a lot better than a calculator.
...just my two bits, and maybe some food for thought.
Thanks for that.... 10kg or 22lbs in 1hr with 440W. Wow. My calcs must be out. 22lbs of chocolate in an hour is a lot. I get the drift re losses but for now I must assume negligible losses. Thanks Brad.
I'm not sure about your calcs. However the white ACMC tempering machines hold about 10 lbs of chocolate, and use two clear 110 watt light bulbs for heat, and no fan to circulate the air while heating. They melt the chocolate and heat it to 123 degrees F from our ambient room temperature of 64 degrees F, in almost exactly one hour. It then takes almost exactly one hour to run the machine through the rest of it's tempering cycle.
Like I said, my staff do this every morning, and do it with several of these machines at a time.
Interestingly enough, it takes almost the same time to cycle through the dark chocolate as it does the milk chocolate with those machines. The milk does however take a few minutes longer for each cycle.
I ran a quick test today on some milk chocolate i had handy. I won't give any specifics on it's formulation, but at 19C - 1589 J/KgC (or 0.378 Btu/lbF). If I were you, I'd increase that a bit for your chocolate.